1 Answer
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A word whose letters can be found sequentially on a regulation dartboard whose numbers have been converted into A1Z26. Acceptable moves between letters/numbers include (1) moving to the next letter/number clockwise, (2) moving to the next letter anti-clockwise, (3) moving through the bullseye to the letter/number directly opposite, and (4) staying on the same letter/number for a second use.

TARD, JOB and NILE are found clockwise.
TELL is found anti-clockwise.
BOIL, OIL and JOIN are made by leaping across the bull from O to I.
BLINK is made by leaping across the bull from B to L.
ARGS is made by leaping across the bull from R to G.
GRATE is made by leaping across the bull from G to R.

As for the name:

In darts, the dartboard is the TARGET.

And the clue...

A 'white horse' is a darts term in the 'Cricket' variant of the game, when a player hits 3 different scoring trebles with their first set of 3 darts...